HENDRA VIRUS RESURFACES
Horse Infected in Australian Outback
By: John V. Wood
Ten years after a deadly virus found only in Australia was first discovered, once again it rears
its ugly head. A horse near the Townsville area of Australia was diagnosed with Hendra
virus, a deadly equine morbillivirus, on December 14, 2004. The horse was later destroyed.
A short time earlier, a veterinarian in the Cairns area was diagnosed with a mild case of the
Hendra virus, and later recovered.
Hendra virus, to this date, has only been found in Australia, and there have only been five
reported outbreaks of this deadly virus. The host of the virus appears to be fruit bats
indigenous to Australia. According to Liz Smith, corporate communications director for
Australia’s Department of Primary Industries and Fisheries, the outbreaks have coincided
with fruit bat breeding seasons.
Smith also says the signs of Hendra virus infection, for the most part, are easily identified.
“Signs to look out for in horses include respiratory distress, frothy nasal discharge, elevated
heart rates and increased body temperatures,” says Smith. “Some neurological changes like
head-pressing or twitching have occurred, and some cases have been initially thought to be
colic.”
One factor that makes Hendra virus more potent is the fact it is a zoonotic disease, or a
disease that is shared or transmitted between animals and humans. Dr. Christopher Olsen
DVM PhD, associate professor of public health and expert in veterinary virology at the
University of Wisconsin – Madison, believes there are unanswered questions about how the
virus is transmitted.
“There are still a lot of questions about the virus. It does affect both the respiratory tract and
the central nervous system, so it’s likely that it can be aerosolized, but the exact routes of
transmission have not been proven at this point,” says Dr. Olsen. “This is a very interesting
virus in the sense that there have really only been a very small number of specific outbreaks
and confirmed infections, so this is not a virus that is circulating widely within the horse
population, even in Australia.”
Luckily, the Hendra virus is not aggressively contagious. “Horses are probably infected by
eating fruit bat material contaminated with the virus,” says Smith. “Transfer of the virus to
humans has only occurred through direct contact with infected horses. There is no evidence
of person-to-person transmission of the disease.”
For North American horse owners, Dr. Olsen has some words of encouragement. “I think the
very important thing to realize is this is not a virus that has ever been recognized or detected
as a pathogen that is circulating in North America,” says Dr. Olsen. “I think horse owners in
the United States, at this point, have very little reason for concern.”
